The invention relates to a process for the removal by absorption of noxious compounds from waste gases, particularly gases generated by the combustion of industrial or domestic wastes.
For this purpose several processes are known which either operate with dry or with wet residues.
The wet residue processes require additional purification steps since the waste water formed connot readily be recycled into the fresh water channel. These processes therefore involve substantial additional apparatus which again increases the cost of the process.
The processes operating with dry residues either apply finely ground absorbents in dry condition to the gas or spray-inject a neutralizing agent together with water into the waste gas flow or establish the contact in some other way.
It is for instance known from German published application No. 2,518,079 to spay-inject a neutralizing agent with water into the waste gas stream and then to subject the gas stream to chilling in order to form dry salts. The volume of the injected water is determined on the basis of the flow rate and the temperature of the waste gas which heats up and causes its evaporation. The concentration of the neutralizing agent in the water is such that the neutralizing agent is present in amounts which at least are equivalent to the stoichiometric amount necessary for reacting with all of the noxious gases.
In view of the continuous changes in operating conditions continuous adjustments are necessary to comply with the specific conditions. These adjustments are costly and are normally effective only with a certain phase lag. An economically optimum and at all times satisfactory absorption of the pollutions is not assured thereby.
It is therefore an object of the present invention to obtain an adjustment of the injected water and of the added neutralizing agent in a continuous manner and without a phase lag and in accordance with the conditions prevailing at any moment of time and thus to obtain a uniform quality of the purified gas while minimizing the amount of necessary neutralizing agent.